1. Field of the Invention
The present invention relates to a production method for nanomaterials, and more specifically to a method of producing a three dimensional nanostructure using a template with a very fine pattern formed thereon, as well as a metal oxide nanomaterial forming composition and a template used in such a method, and a metal oxide nanostructure.
Priority is claimed on Japanese Patent Application No. 397467, filed Nov. 27, 2003, Japanese Patent Application No. 427386, filed Dec. 24, 2003, and Japanese Patent Application No. 91414, filed Mar. 26, 2004, the contents of which are incorporated herein by reference.
2. Description of Related Art
Nanomaterials comprising a metal oxide with a three dimensional nanostructure, or nanomaterials comprising a composite material of an organic compound and a metal oxide with a three dimensional nanostructure display different physical and chemical characteristics from the corresponding bulk materials, and are consequently attracting considerable interest in terms of both fundamental research and applied research. For example, nanomaterials with a hollow three dimensional structure are expected to prove extremely useful in a wide variety of fields, including inclusion chemistry, electrochemistry, material science, biomedicine, sensors, catalysis and separation technology.
The template method is a conventional technique used for producing nanomaterials. In the template method, fine template particles are dispersed in a solvent, and once the surface of these fine template particles have been coated with a thin membrane, the fine template particles are removed, thereby producing a spherical capsule shaped nanomaterial with a hollow three dimensional structure (for example, see the non-patent reference 1). However in this method, the formation of nanosize template particles capable of dispersion within a solvent is problematic, and when designing the template particles, there is little freedom in terms of the shape of the three dimensional structure.
On the other hand, methods of fabricating three dimensional structures directly using laser stereolithography are also known (for example, see non-patent reference 2). However in these methods, the size of the pattern fabricated on a solid substrate is in the micrometer range, and the fabrication of nanosize structures is almost impossible, meaning these methods cannot be used for further size miniaturization.
In response to these problems, the inventors of the present invention have proposed a method of producing a nanomaterial with an ultra thin three dimensional membrane structure by coating the surface of a template with a nanopattern formed thereon with an ultra thin titania film, and then removing the template (see non-patent reference 3).
(Non-patent reference 1) Frank Caruso, “Nanoengineering of particle surfaces”, Advanced Materials 13(1), pp. 11-22 (2001).
(Non-patent reference 2) Marc J. Madou, “Fundamentals of Microfabrication: The Science of Miniaturization”, second edition, CRC Press (USA), pp. 66-67.
(Non-patent reference 3) “Polymer Preprints, Japan”, published May 8, 2003, vol. 52 (2003), No. 3, p. 471.
The method disclosed in the above non-patent reference 3 permits a high degree of freedom in terms of the template shape, although it is still somewhat satisfactory in terms of reproducibility and reliability, so that depending on the template material, an ultra thin three dimensional film structure of favorable shape may not be achievable.